Rams will not get over 4". Most males stay around 3.5", while females around 3". They are very sensitive to water quality, espically water hardness. They need very soft water to thrive. Rams should not eat plants, and should be peaceful to most fish you plan on adding. I doubt they would eat any shrimp as well, but if there is like baby shrimp, then they cant refuse.
They also get very friendly, and some can recognize their owners. However, they usually only live for 2-3 years, which is short compared to plenty of other fish on the market. I do reccomend them, and you can build a very nice planted South American biotope around them when placed with the proper tankmates.